A. Field of Invention
This invention pertains to the art of methods and apparatuses for flexible drive shafts for rotary power tools and more particularly to a flexible drive shaft with a connector that allows interchange of driven working ends.
B. Description of the Related Art
Flexible shafts comprise basic elements of power transmission and are designed to transmit power or control from a driving element to an element to be driven. Transmission may be over, under, or around obstacles or objects where transmission by solid shafts would be impractical or impossible.
In a typical rotatable flexible shaft, a wire mandrel has a plurality of layers of closely coiled wire wound thereover, each of the layers being successively wound over another in alternately opposing directions, i.e., right or left-hand lay. This shaft is usually covered by a flexible casing, metallic or covered, and a clearance between the shaft and casing is provided in order that the shaft may rotate freely within the casing.
Rotatable flexible shafts are of two basic types—power driven and remotely controlled. Power driven flexible shafts are designed primarily for motor-driven or high-speed operation in one direction. Remote control flexible shafts, on the other hand, are designed primarily for hand-operated control in either direction.
Power driven flexible shafts have two general classes of application—those in which there is relative movement between the driving and driven elements, and the curvature and twisting of the shaft is continually changing, as when, for example, a driven element such as a portable grinding tool is continuously moved about the workpiece by an operator and those in which the shaft operates in a given position and the curve, or curves, of the shaft remain substantially fixed, as in the coupling arrangement of the present invention wherein a shaft is used to transmit torque from a motor to a trimmer, for example. In a typical arrangement of this type, a fitting is permanently affixed to each end of the flexible shaft and the fitting suitably respectively connected to the output shaft of the motor and input shaft of the driven member.
It is known in the art to use a flexible drive shaft in a rotary power tool, such as a flexible line trimmer. It is also known in the art to include a connector-type connection that allows for the attachment of any one of many different driven working member to the rotary power tool.
One problem with existing flexible drive shaft connections is the tendency for the connection to “strip” or break with use. Another problem with the existing connection designs is that it is difficult to effectively and completely insert the working member into the connection. This causes improper performance of the combination and can result in damage to the connection and/or drive shaft.
The present invention provides for a flexible drive shaft with an improved connector connection for rotary power tools.